When plastic containers are utilized to retain liquids such as oil or water, it has been found that it is necessary that the closure utilized with the container have a separate liner in order to provide an adequate seal. The problem of sealing is made even more complex where the plastic container is made by closing molds about a tube of molten plastic material and blowing the tube followed by thereafter cutting and trimming the portion of the tube that has been blown into a finish to provide a sealing surface on the upper end of the finish. The trimming process often results in variation in the plane of the finish at circumferentially spaced points along the sealing surface as well as non-uniformity in a radial direction. The trimming process can result in variations in height circumferentially of the finish, known as "trim slant". The trimming can also result in the top surface being inclined rather than being perpendicular to the longitudinal axis of the container. In addition, in such a molding process wherein the tube is extruded variations in diameter of the finish can occur circumferentially known as ovality. Each of these conditions can result in failure of the seal so that it has thought to be necessary to utilize a sealing liner in the closure. Sealing on such a container is also made more difficult due to variations or imperfections in the seam produced adjacent the juncture of the closed molds.
Various patents have been proposed including flanges extending radially outwardly and inwardly as shown in U.S. Pat. Nos. 3,053,406, 3,067,900, 3,255,909, 3,393,818 3,802,590, 4,069,937, 4,196,818, 4,220,250, 4,398,645, 4,422,947, 4,450,973, 4,598,835, 4,739,893 and 4,872,304.
As far as the present inventor is aware, none of these patents has been directed to the problems of the present invention or resulted in a satisfactory package for liquids.
Among the objectives of the present invention are to provide a package for a plastic container made by the aforementioned process which does not require a separate liner and utilizes a linerless sealing closure system which will compensate for any unevenness and out-of-round top surfaces on the finish of the container; and which container package will be capable of packaging oil, water or similar fluids.
In accordance with the invention a plastic container closure package with a linerless sealing closure system comprising a plastic container having a threaded finish for receiving a closure having a base wall and an internal skirt with complementary threads on the skirt. The plastic container is made by a process wherein a tube of molten plastic is inflated and blown to form the container and thereafter the tube is trimmed to form the sealing surface of the finish of the container. The closure includes an annular flange that extends downwardly from the underside of the base wall of the closure and radially inwardly of the closure for engagement with the sealing surface on the container. The annular flange includes a smooth continuous frustoconical surface that faces the finish of the container and engages the inner edge at the juncture of the top surface and inside surface of the finish of the container. An annular stop extends axially from the underside of the base wall of the closure to limit the flexing of the annular flange. The width of the flange is such that the free end thereof normally extends beyond the inner edge of the finish surface into sealing engagement intermediate the free edge and the end of the flange.